quan is shopping. he can buy 2 pants and 1 shirt for $79.85 (before tax is added). he can but 1 pair of pants and 2 shirts for $69.85 (before tax is added). how much does a shirt cost?

a)$29.95
b)$10.50
c)$19.95
d)$5.50

and the answer that i picked is b
thanks